In recent years, the organic light-emitting displays are widely used in many consumer electronic products due to those advantageous characteristics, such as self-luminescence, wide viewing angle, high response speed, high color saturation and flexile panels. Generally, an organic light emitting display includes a plurality of light-emitting units formed on a substrate, and each light-emitting unit includes two electrodes (such as a metal cathode and an ITO anode) and a light-emitting organic material sandwiched therebetween. A control circuit provides signals to control the light-emitting units so that the organic light-emitting device can display image.
FIG. 1A is a cross-sectional view of a conventional organic light-emitting device 10. In FIG. 1A, in a pixel area 1, a cathode layer 11 of the organic light-emitting device 10 is formed over an anode layer 12, an organic light-emitting layer 13, and an pixel definition layer 14. The cathode layer 11 is typically a thin metal layer with a thickness about 10 to 200 angstroms. Generally, the cathode layer 11 is extended to contact a signal layer 15 in a peripheral circuit area 11 in order to inhibit voltage drop, and in turn, prevent variation of display luminance. However, the cathode layer 11 in the peripheral circuit area 11 is prone to damage (i.e. broken) because the aspect ratio of the contact hole 16 is too high and the cathode layer 11 is too thin. FIG. 1B is a cross-sectional view of another conventional organic light-emitting device 100 in the related art. An auxiliary electrode is employed between pixels in a pixel area and electrically connected to an electrode layer of the light-emitting units to inhibit the voltage drop. As shown in FIG. 1B, the organic light-emitting device 100 includes a transistor unit 104 on a bottom substrate 102, a first electrode layer 106 (such as an anode) in a pixel area electrically connected to the transistor unit 104, the auxiliary electrode 108, a pixel definition layer 110, an organic light-emitting layer 112, a second electrode layer 114 (such as a cathode) on the organic light-emitting layer 112, a planarization layer 116, a filter layer 118, and an upper substrate 120. The cathode 114 is electrically connected to the auxiliary electrode 108 to ensure the electrical connection intact even if the electrode is damaged. However, this kind of organic light-emitting device also has some drawbacks. For example, every pixel needs to sacrifice certain areas to serve as contact regions of the cathode electrode 114 so that the available light-emitting area is decreased, and the resolution and the possible shrinkage of the display are restricted.
Thus, it is desired to have an organic light-emitting device which can avoid the broken electrode issue without decreasing the light-emitting area, and a method of forming the same.